Showers in outdoor runs of organic growing-finishing pigs: effects on behaviour, soiling and skin surface temperature

Summary

For pigs kept in organic housing systems with access to concrete outdoor runs, showers may be increasingly important to alleviate heat stress. Additionally, they could reduce faecal soiling of pigs and increase the use of outdoor runs. Therefore, we conducted experiments on three commercial organic farms in Austria (AT) and Switzerland (CH), including 4-6 pens of growing-finishing pigs per farm (total of 428 pigs). In half of the pens, we installed showers (mist-like sprinklers, flow rate 1.0- 2.4 l/min) in the outdoor run, which were running 5-6 times per day for 30 minutes, followed by a 30- or 60-minutes break. On 2-3 days with temperature exceeding 22°C, we conducted behavioural observations in the outdoor run, inspected pigs for soiling and took pictures with a thermal imaging camera on group-level during and between shower activation (same schedule for control pens). We calculated skin surface temperature differences of the time before and during the shower. Data were analysed with linear mixed effect models with treatment as fixed effect. Results indicate a decreased proportion of pigs in outdoor runs with shower (48%) compared to control pens (61%, p=0.02). Pigs with a shower were lying less laterally (p=0.001), while lying in contact with pen mates was not affected by treatment (p=0.12). Pigs with access to a shower were not cleaner than pigs in control groups (p=0.15). The skin surface temperature of pigs with access to showers was reduced during shower activation by 1.3 and 2.2°C in AT and CH, respectively, while temperature did not differ in control groups. The effect was significant in CH (p=0.02) and a tendency in AT (p=0.08). We conclude, that installing showers in the outdoor run can improve pig welfare by reducing heat stress under practical conditions.